Pumps

ABSTRACT

A peristaltic type pump comprises a reciprocating pumping element which alternately pinches and releases a flexible-walled tube, and, on either side of the pumping element, reciprocating inlet and outlet closure elements respectively. When the pumping element pinches the tube during a pumping stroke the inlet closure element pinches the tube to close it while the outlet closure member releases the tube, and during induction strokes, as the pumping element releases the tube, the inlet closure element is open, while the outlet element is closed. Synchronised operation of the elements is conveniently effected by respective cams.

United States Patent Pulman et al.

[ 51 Apr. 25, 1972 [541 PUMPS [72] inventors: Prockter T. Pulman; Geoffrey D. S. Horsiall, both of Rainbow Valve Company Limited, Upthorpe Road, Staton, Bury St. Edmunds, Suffolk, England [22] Filed: June1l,l970

[21] Appl.No.: 45,488

2,689,530 9/1954 Harvey ..4l7/474 2,922,379 l/l960 Schultz... ...4l7/475X 2,412,397 l2/l946 Harper ..4l7/474 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney-Michael S. Striker [57] ABSTRACT A peristaltic type pump comprises a reciprocating pumping element which alternately pinches and releases a flexiblewalled tube, and, on either side of the pumping element, reciprocating inlet and outlet closure elements respectively. When the pumping element pinches the tube during a pumping stroke the inlet closure element pinches the tube to close it while the outlet closure member releases the tube, and during induction strokes, as the pumping element releases the tube, the inlet closure element is open, while the outlet element is closed. Synchronised operation of the elements is conveniently effected by respective cams.

13 Claims, 13 Drawing Figures lJ: I: 19 11-1116 m I LU] (2L1 I PATENTEUAPR 25 m2 3 658 ,445

SHEET 2 UF 5 PATENTEDAPR 2 5 m2 SHEET 3 OF 5 Wwr PATENTED PRZ IHYZ 3 658,445

SHEET MF 5 Fig. 8.

PUMPS This invention relates to pumps, more particularly pumps of the peristaltic type in which a fluid is pumped along a flexible walled tube by cyclic deformation of the'tube.

Known types of peristaltic pump include pumps in which cyclic deformation of a flexible walled tube is effected by means of rotary cams. It is not generally possible to vary the output of such known peristaltic pumps over a wide range such variation is usually effected by changing the speed of rotation of the cams, and this is difficult where a.c. motors are used for driving the cams.

An object of the present invention is to provide a pump of the peristaltic type which is suitable for pumping fluids, particularly liquids, in accurately metered quantities, and the output of which is, preferably, variable over a wide continuous range.

According to the present invention there is provided a pump comprising a pumping element cooperating with a portion of a flexible-walled tube, an operating member for reciprocating the pumping element so as cyclically to pinch and release the tube to effect pumping and induction strokes successively, and inlet and outlet closure elements mounted on either side of the pumping element for reciprocation, under the control of respective operating members, between closed positions in which they pinch the tube to prevent flow therethrough and open positions in which they permit flow through the tube, the said operating members being so arranged relatively to each other that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element is its closed position.

The pump according to the invention is preferably provided with means for varying the stroke of the pumping element so as to vary the pump output at will. In a preferred embodiment of the invention the pumping element is carried by a lever arm which is resiliently biassed to urge the pumping element into engagement with the tube, the respective operating member comprising a rotary cam engaging said lever arm to rock the latter in opposition to its resilient bias to reciprocate the pumping element upon rotation of said cam. In this embodiment the stroke adjustment means may comprise an adjustable stop engageable with said lever arm to arrest pumping movement thereof at a predetermined position in each cycle of rotation of the rotary cam, limiting the deformation of the tube effected by the pumping element.

Using stroke adjustment means of this type it is possible to vary the pump output over a wide range, typically by a ratio of about I511. The range can be further increased by incorporating a variable speed gear in the drive to the cams.

The pump according to the invention is ideally suited for pumping contaminated fluids, since none of the moving parts of the pump come into contact with the pumped fluid in the flexible walled tube. Also, since there are no line clearances or restrictions in the flow passage through the pump (that is, the bore of the tube) the pump is extremely tolerant of the presence of grit or other solid bodies in the fluid to be pumped.

In a preferred embodiment of the invention the pumping element comprises a pad extending generally in the longitudinal direction of the flexible tube and having on its tube-engaging face a transverse rib which engages the tube in each pumping cycle before the remainder of the pad so that in a position of the adjustment means for minimum pumping stroke only the transverse rib engages the tube in each pumping cycle. By this means it is possible to adjust the pump delivery to a very small value if desired. This is particularly useful where the pump is used to supply small metered quantities of an additive to a bulk liquid, for example metered quantities of a liquid drug to a livestock drinking water supply.

The inlet and outlet closure elements are preferably carried by respective lever arms which are resiliently biassed to urge the closure elements into pinching engagement with the tube, the respective operating members for the closure elements comprising respective rotary cams engaging said lever arms to rock the latter in opposition to their resilient bias to effect reciprocation of the closureelements upon rotation of the cams. Each said closure element may be pivotally attached to its respective lever arm for rocking movement about an axis generally parallel to the pivotal axis of the lever. Preferably the respective lever arms are mounted for rocking movement about a camshaft. Moreover, the said cams are also preferably mounted on a common rotary camshaft.

The portion of flexible walled tube cooperating with the pumping element and the closure elements is conveniently supported on an anvil surface against which the tube is pressed when engaged by the pumping element and the respective closure elements.

In a preferred embodiment of the invention the anvil surface is provided on an anvil member around which the flexible-walled tube may be passed so that said portion of the tube lies on the anvil surface, the tube and the anvil member being removable as a unit from a housing containing the pump. In this embodiment the portion of flexible walled tube may be easily removed from the pump by withdrawing the removable anvil member, thereby facilitating replacement of the flexible walled tube as required.

When the pump is not in use it is desirable that the flexible walled tube should be undeformed, as leaving the tube in a flattened or pinched state for any length of time could, with some tube materials, lead to a permanent deformation of the tube or sticking together of the internal surfaces of the tube. The pump is therefore preferably provided with an eccentric release cam means which are rotatable to effect simultaneous movement of the pumping element and the two closure elements out of engagement with the tube, to facilitate replacement of the tube, said release cam being out of engagement with pumping and closure elements, or the operating means therefor, in normal operation of the pump.

The anvil member is preferably provided with means engageable by a latching device for retaining the anvil member in its correct position of insertion in said housing.

In one preferred embodiment of the invention the pivot axis of the or each lever arm is disposed between the respective pumping element or closure element and that part of the lever arm which engages the respective rotary cam. I

The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a top plan view of a pump according to one embodiment of the invention;

FIG. 2 is a sectional view of said pump taken on the line II- II of FIG. 1;

FIGS. 3A, 3B and 3C are respectively bottom plan, side elevational and end elevational views of the pumping element in the pump of FIGS. 1 and 2;

FIGS. 4A, 4B and 4C are respectively top plan, side elevational and end elevational views of one of the closure elements of the pump of FIGS. 1 and 2;

FIG. 5 is a diagrammatic perspective view of a pump according to the invention complete with its housing, illustrating a modification facilitating replacement of the flexible walled tube of the pump;

FIG. 6 is a side elevation of an anvil member forming part of the pump of FIG. 5.

FIG. 7 is an end elevation of the anvil member in the direction of arrow VII of FIG. 6;

FIG. 8 is a sectional view of a pump according to an alterna' tive embodiment of the invention, taken on line VIII-VIII of FIG. 9;

FIG. 9 is a fragmentary top plan view of part of the pump shown in FIG. 8.

The same reference numerals are used throughout the drawings to indicate the same or corresponding component parts.

Referring to FIGS. 1 and 2 the pump according to the invention has a baseplate 1 provided with two upstanding parallel side walls 2. A removable cover 3 (FIG. is adapted to be fitted on the baseplate 1 between the side walls 2 to complete the pump housing. The cover 3 is omitted from FIGS. 1 and 2 for the sake of clarity.

A solid anvil 4 upstands from the baseplate 1 and extends transversely between the side walls 2. The anvil 4 has a flat anvil surface 5 upon which a portion of flexible-walled tube 6 is supported. The flexible-walled tube 6, which is formed of any convenient resilient material such as rubber or plastics, enters the pump housing through a hole in one of the side walls 2 and leaves through a hole in the opposite side wall 2, as shown in FIG. 1.

A pumping element 7 cooperates with the central portion of the flexible-walled tube 6 supported on the anvil surface 5. The pumping element 7, which is shown in detail in FIG. 3, comprises a generally rectangular pad 8 extending in the longitudinal direction of the flexible-walled tube 6 and having flared end portions 9 (FIG. 3C) which are curved away from the tube 6 to prevent the element 7 from cutting into the tube 6 when it is engaged therewith. The pad 8 is provided on its tube-engaging surface with a central rib 10 extending transversely to the axis of the tube 6.

The pumping element 7 is carried by a lever arm 11 which is pivotally supported at one end on a shaft 12 extending between the side walls 2 in a direction generally parallel to the axis of the tube 6. Near its other end, that is, on the side ofthe pumping element 7 remote from the shaft 12, the lever arm 11 is engaged by a helical biassing spring 14 which is maintained under tension between the lever arm 11 and an adjustable screw anchorage 15 located in the baseplate 1. The spring 14 biasses the lever arm 11 in a counter-clockwise direction of rotation about the shaft 12 as viewed in FIG. 2, urging the pumping element 7 into engagement with the flexible walled tube 6, and at the same time urging a cam follower plate 16 carried by the lever arm 11 into contact with the surface of a rotary cam 17. The cam 17 is mounted on a rotary camshaft l8 jornalled in the side plates 2 and extending parallel to the shaft 12. Means 11, 14, 17 are operating means for element 7.

The cam 17 is so shaped that upon rotation of the camshaft 18 the lever arm 11 is cyclically raised against the action of the biassing spring 14, lifting the pumping element 7 cyclically out of engagement with the tube 6.

An adjustable stop 19 is supported by means ofa screw 20 in the baseplate 1 in the path ofrocking movement ofthe lever arm 11 about the shaft 12. The stop 19 is adjustable, by means of a thumb wheel 21, relative to the free end of the lever arm 11.

Respective inlet and outlet closure elements 23, 24 are supported by respective lever arms 25, 26 above the anvil surface 5 on opposite sides of the pumping element 7 for movement into and out of pinching engagement with the tube 6 at inlet and outlet ends respectively of the latter. Each lever arm 25, 26 is pivotally supported at one end on the shaft 12 and is engaged at its opposite end, outwardly of the respective closure elements 23, 24 by a respective helical biassing spring 27, 28 (FIG. I) which is maintained in tension between the respective lever arms 25, 26 and the baseplate 1 similarly to the biassing spring 14.

The respective lever arms 25, 26 carrying the closure elements 23, 24 are urged by the biassing springs 27, 28 into engagement with respective earns 29, 30 mounted on the camshaft 18, the lever arms 25, 26 contacting the surfaces of said cams by way of respective cam follower plates 31, 32, generally similar to the cam follower plates 16, so as to reduce friction and wear at the points of contact of the lever arms with the cams. Means 25, 26, 27, 28, 29, 30 are operating means for the elements 23,24.

The two closure elements 23, 24 are substantially identical one of said elements, 23, being shown in detail in FIG. 4. Each closure element 23, 24 comprises a generally U-shaped member arranged with its convex outer surface towards the flexible-walled tube 6 and pivotally attached to the respective lever arm 25, 26 by way of transverse pivot pin 33, 34 extending parallel to the axis of the shaft 12 and passing through the side walls of the respective U-shaped element. The pivotal mounting of the closure elements 23, 24 on their respective lever arms 25, 26 enables these elements to accommodate local non-uniformities in the wall thickness ofthe tube 6, and any lack of parallelism between the underside of the respective lever arms 25, 26 and the anvil surface 5. This ensures that the walls of the tube 6 are tightly pinched together, sealing the internal flow passage of the tube, when the latter is engaged by the elements 23, 24.

The cams 17, 29 and 30 are angularly arranged relatively to each other on the camshaft 18 so that upon rotation of the latter (in a clockwise sense as viewed in FIG. 2) the lever arms 25, 11 and 26 are raised in succession, and subsequently lowered under the action ofthe respective biassing springs 27, 14, 28in each cycle of rotation ofthe camshaft 18.

In order that the respective biassing springs 14, 27 and 28 may exert their full effect in urging the pumping element 7 and the respective closure elements 23, 24 into engagement with the flexible-walled tube 6 the base-circle diameters of the cams 17, 29 and 30 are such that at the position of closest approach of the respective elements 7, 23 and 24 to the anvil surface 5, corresponding to maximum compression of the flexible-walled tube 6, the respective cams I7, 29 and 30 are out of contact with the respective cam follower plates 16, 31 and 32. In this position the respective closure elements 23, 24 pinch the walls of the tube 6 together, effectively closing the tube and preventing liquid flow therethrough. The extent to which the tube 6 is compressed by the pad 8 of the pumping element 7 in this position will, however, depend on the adjustment of the stop 19. The stop 19 serves the arrest the respective lever arm 11 at a predetermined position as it moves the pumping element 7 towards the anvil surface 5 under the ac tion of the biassing spring 14.

As the camshaft 18 rotates the sequence of operations in one complete pumping cycle is as follows, starting from the condition in which the elements 7, 23 and 24 are all at their positions of closest approach to the anvil surface 5, in engagement with the flexible walled tube 6:

i. The lever arm 25 is raised by the cam 29, lifting the inlet closure element 23 out of engagement with the tube 6.

ii. The lever arm 11 is lifted by the cam 17, raising the pumping element 7 clear of the central portion of the tube 6, so that the liquid is drawn into this portion of the tube 6 as the latter expands.

iii. The lever arm 25 drops, following the surface of the cam 29, under the action ofits biassing spring 27, bringing the inlet closure element 23 into pinching engagement with the tube 6 and closing the inlet end of the latter.

iv. The lever arm 26 is raised by the cam 30, lifting the outlet closure element 24 out of engagement with the tube 6, thereby opening the outlet end of the tube.

v. The pumping element 7 moves towards the anvil surface 5 under the action of its biassing spring 14, compressing the tube 6 and expelling liquid therefrom through the open outlet end.

vi. The outlet closure element 24 descends under the action of its biassing spring 28, sealing the outlet end of the tube 6. Both the inlet and outlet ends of the tube are now closed and the pump then begins a further pumping cycle. Since the inlet and outlet closure elements 23, 24 operate to close the inlet and outlet ends of the tube 6 in each cycle of the pump the quantity of liquid expelled in each cycle through the outlet end of the tube is accurately controlled by the amount of deformation of the central portion of the tube 6 effected by the pumping element 7. This in turn is precisely adjustable by means of stop 19, so that the pump is ideally suited for use as a metering pump for supplying at regular intervals accurately metered quantities of a liquid to be pumped.

If the adjustable stop 19 is positioned so that the pumping element 7 in its closest approach to the anvil surface 5 engages the tube 6 only with the transverse rib l the deformation of the tube 6 is very small and in consequence the pump delivery is very small. The pump therefore affords easy adjustment over a wide range of outputs.

The delivery of the pump may be further adjusted by means of variable gearing (not shown) in the transmission 'to the camshaft 18. For example, thecamshaft 18 may be driven by an electric motor through suitable reduction gearing including replaceable or adjustable elements for varying the speed of rotation of the camshaft 18.

To facilitate replacement of the flexible-walled tube 6 and to ease the strain on the tube '6 when the pump is not in use an eccentric release cam 35 is provided. The cam 35 is supported on a transverse shaft 36 extending between the side walls 2 parallel to the shafts 12 and 18. The shaft 36 can be rotated by means of a hand lever (not shown) through 180 to bring the cam 35 into simultaneous engagement with the under sides of the levers 11, 25 and 26, lifting'these levers against the action of their biassing springs 14, 27 and 28 so that the respective elements 7, 23 and 24 carried thereby are lifted clear of engagement with the tube 6. The tube 6 can then be removed for cleaning or replacement.

The insertion and removal of the flexible-walled tube "6 is facilitated in the modification illustrated in FIGS. to 7. In this modification the anvil surface 5 is provided on a removable anvil member 4A which can be inserted in the pump housing from one side thereof through a suitable opening 4B in one of the side walls 2. For ease of illustration FIG. 5 shows the anvil member 4A in its removed condition.

The flexible walled tube 6 passes over the anvil surface 5 in the same manner as in the embodiment of FIGS. 1 and 2 but then loops around a semi-circular end surface of the anvil member 4A and returns along a lower surface thereof which is parallel to the anvil surface 5. The inlet and outlet ends of the tube 6 are located in respective keyhole-shaped notches 37, 38 (FIG. 7) provided in a plate 39, attached to one end of the anvil member 4A. The size of the plate 39 is such that, when the anvil member 4A is fully inserted into the pump housing the plate 39 is located against the sides of the aperture 43 preventing insertion of the anvil member 4A beyond its correct position in the pump housing. When the anvil member 4A is fully inserted, its semi-circular end surface projects beyond the side wall 2 remote from the plate 39, both said side walls, which are shown in broken outline in FIG. 6, being provided with similar openings 4B (one only of which is visible in FIG. 5). The side of the anvil member 4A is provided with a slot 40 with which a latching element or detent 40A is engageable to retain the anvil member 4A in position in the pump housing during operation of the pump. A small knob 41 affixed centrally to the plate 39 facilitates withdrawal and insertion of the anvil member 4A.

In the illustrated embodiment the anvil member 4A has cheek plates 42 on opposite sides, the plates 42 defining between them a circumferential channel in which the part of the tube 6 which passes around the anvil member 4A is located, the tube 6 being omitted in FIGS. 6 and 7 for the sake of clarity. The anvil surface 5 on the upper flat surface of the anvil member 4A is therefore bounded by upstanding flange portions 43 of the cheek plates 42. These flange portions 43 are provided with cutout regions 44 at appropriate positions to allow the lever arms 11, 25 and 26 to act upon the respective portions of the tube 6 without interference.

FIGS. 8 and 9 illustrate a modification of the pump shown in FIGS. 1 and 2, incorporating an alternative arrangement, combining the functions of the adjustable stop 19 and the release cam 35 of FIGS. 1 and 2. In FIGS. 8 and 9, each of the lever arms 11, 25 and 26 is extended beyond the points of attachment of the respective springs 14, 27 and 28. The extended ends of the lever arms 11, 25, 26 are held by the respective springs 14, 27, 28 in contact with respective presettable earns 45, 46, 47 which are mounted on a common adjuster shaft 48. The shaft 48 is journalled at opposite ends in the respective side plates 2, and projects outwardly of said side the shaft 48 towards the internal surface of the internal surface of the rear side plate 2. A friction washer 53, for example of paper, is located between the plate 52 and the rear plate 2 to cause a frictional resistance, adjustable by means of the nut 50, to rotation of the shaft 48 by means of the knob 49. This prevents rotation of the shaft 48 from any adjustment setting.

The pre-settable cams 46 and 47 are identical and each has a symmetrical, single-lift profile, the cam 46 being shown in broken outline in FIG. 8. Between the earns 46 and 47, the cam 45 has a profile which combines a snail cam portion 45A, of progressively decreasing radius, extending over 270, as visible in FIG. 8, and a lift cam portion 458, not visible in FIG. 8, being identical to the cams 46 and 47, the minimum radius of the snail cam portion 45A merging smoothly with the start of the lift cam portion 45B.

When the knob 49 is in the setting shown in FIG. 8, the lever arm 11 contacts the maximum radius part of the snail cam portion 45A, and reciprocation of the arm 11 is prevented: this setting therefore corresponds to zero pump output, As the knob 49 is progressively turned in a clockwise direction (as viewed in FIG. 8), the permitted stroke of the lever arm 11 increases, maximum pump output corresponding to the minimum radius part of the snail cam portion 45A, after rotation of the knob 49 through 270.

Further, rotation of the knob 49 clockwise brings the lift cam portion 493 into engagement with the lever arm 11 and, simultaneously, the cams 46, 47 into engagement with the respective lever anns 25, 26. All three lever arms 11, 25 and 26 are thereby lifted together, releasing the flexible tube 6 for replacement thereof if required.

A graduated scale may be provided on the external surface of the side plate 2 underlying the knob 49 to indicate, in cooperation with a pointer or mark on the knob 49, the setting of the knob 49.

Where, as previously described with reference to FIGS. 5 to 7, a removable anvil member 4A is provided, suitable means (not shown) may be arranged for cooperation with, for example, the upper surface of the lever arm 25, to release the anvil retaining latch 40A from slot 40 the anvil member 4A in position when the arm 25 is lifted clear of the tube 6.

In the embodiment of FIG. 8, the arrangement of the pump components is also modified so as to arrange the operating cams 17, 2 9, 30 at one end of the respective lever arms 11, 25, 26, remote from the ends thereof cooperating with the cams 45, 46, 47, the shaft 12 being located between the tube 6 and the cam follower plates 16, 31, 32. This arrangement minimizes the risk of oil, used to lubricate the cam follower plates 16, 31, 32, reaching the tube 6, which could prove troublesome if the tube 6 were of rubber. This arrangement can also be designed with greater overall compactness than that ofFlGS. l and 2.

The pump according to the invention is particularly suitable for supplying metered quantities of an additive liquid such as a drug to a bulk liquid, such as a drinking water supply for broiler house chickens. In such a supply arrangement the additive liquid may be supplied by a metering pump and admixed with the bulk liquid at the inlet of an impeller which circulates the bulk liquid in a closed circuit including a bulk liquid reservoir.

An alternative supply arrangement for livestock drinking water is described in United Kingdom Pat. No. 1,216,087, in which the additive liquid is passed to the suction inlet of an ejector through which the bulk liquid is fed into a reservoir. As applied to such an arrangement the pump of the present invention would be arranged to deliver the additive liquid to the suction inlet of the ejector, admixture with the bulk liquid occuring in the ejector.

In either of these supply arrangements the delivery of bulk liquid to the reservoir is preferably regulated by a float-controlled valve which maintains a substantially constant level of bulk liquid in the reservoir. The float-controlled valve may conveniently be operatively associated with an electrical switch connected in the power supply to the driving motor of the peristaltic pump, so that the latter delivers additive liquid only when the valve is open, admitting bulk liquid to the reservoir.

We claim:

1. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, in combination, a pumping element cooperating with a portion of the flexible-walled tube, said pumping element comprising a pad extending generally in the longitudinal direction of said portion of the flexible tube and having a tube-engaging face, and a transverse rib on said tube engaging face; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump, the rib of the pumping element engaging the tube in each pumping cycle before the remainder of said tube-engaging face of said pad; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position; and stroke adjustment means for varying the stroke of said pumping element, said pumping element engaging the tube only by said transverse rib in the position of said adjustment means corresponding to minimum pumping stroke.

2. Pump as claimed in claim 1, wherein the said first and second operating means include respective rotary cams and respective pivoted lever arms engageable by the rotary cams and carrying the pumping element and the respective closure elements, the pivot axis of each said lever arm being disposed between said portion of said flexible tube and that part of the said lever arm which engages the respective rotary cam.

3. Pump as claimed in claim 1, wherein the pump has a housing and comprises an anvil member having an anvil surface upon which the said portion of said flexible-walled tube lies and against which said tube is pressed when engaged by the pumping element and by the respective closure elements; and means mounting said anvil member in said housing removable as a unit from said housing permitting access to the flexible-walled tube.

4. A pump of the peristaltic type which effects pumping by the deformation ofa flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube, said second operating means including pivoted lever arms, respectively; means pivotally connecting each respective closure element to the respective lever arm for rocking movement about an axis parallel to the pivotal axis of said lever arm; means resiliently biasing said lever arms to urge the respective closure elements into pinching engagement with said portion of the tube, and

rotary cams engaging said lever arms, respectively, and adapted to rock the latter in opposition to their resilient biasing means to effect reciprocation of the closure elements upon rotation of said cams; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position.

5. Pump as claimed in claim 4 wherein the first operating means for reciprocating the pumping element comprise a lever arm carrying the pumping element, means resiliently biassing the lever arm to urge the pumping element into engagement with said portion of the tube and a rotary cam engaging said lever arm and adapted to rock the latter in opposition to said resilient biassing means to reciprocate the pumping element upon rotation of said cam, and a common shaft supporting the respective lever arms of said first, and second operating means for rocking movement about the axis of said common shaft.

6. Pump as claimed in claim 5, including a common cam shaft supporting the respective cams ofsaid operating means.

7. A pump of the peristaltic type which effects pumping b the deformation ofa flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow there through and open positions in which said closure elements permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position; eccentric release cam means; and means rotating said release cam means to effect simultaneous movement of the pumping element and the two closure elements out of engagement with said portion of the tube to facilitate replacement of the tube, said release cam means being out of engagement with said pumping and closure elements during normal operation ofthe pump.

8. Pump as claimed in claim 7, comprising a removable anvil member having a surface upon which rest the portions of the flexible-walled tube engageable by said pumping and closure elements when the anvil member is in a normal operative position; and latching means retaining said anvil member in said operative position, said latching means being releasable automatically when said pumping element and said closure elements are out of engagement with said tube to permit removal of the anvil member.

9. Pump as claimed in claim 7, wherein said first operating means include a lever arm carrying the pumping element; and comprising means for varying the stroke of said pumping element including a presettable rotatable cam engageable with said lever arm, said presettable rotatable cam comprising part of said release cam means and including a common adjusting member operatively connected to both said rotatable cam and the release cam means for selective adjustment thereof.

10. Pump as claimed in claim 7, comprising a housing provided with an opening; a removable anvil member; means mounting said anvil member in said housing removable from said housing through said opening, said anvil member, in its fully mounted position in said housing, supporting the portions of said flexible-walled tube with which said pumping and closure elements cooperate.

11. Pump as claimed in claim 10, wherein said anvil member includes means for retaining said flexible walled tube thereon in contact with an anvil surface of said anvil member, so that the tube is removable for inspection together with said anvil member, when said pumping and closure elements are out of engagement with said tube.

12. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump, said first operating means including a lever arm carrying said pumping element; means resiliently biasing said lever arm to urge said pumping element into engagement with said portion of the tube; a rotary cam engaging said lever arm and adapted to rock the latter in opposition to said resilient biasing means for reciprocating said pumping element upon rotation of said cam, and a presettable rotatable cam engageable with said lever arm and determining the stroke of said pumping element in operation of the pump; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position.

13. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted to either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position, a housing enclosing said pumping and closure elements and provided with an opening; a removable anvil member; means mounting said anvil member in said housing slidable into and slidable out of said housing through said opening, said anvil member, in its fully mounted position in said housing, supporting theportions of said flexible-walled tube with which said pumping and closure elements cooperate, and means on said anvil member for retaining said flexible-walled tube in contact with said anvil surface, whereby the length of said tube with which said pumping and closure elements cooperate is removable from said housing along with said anvil member. 

1. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, in combination, a pumping element cooperating with a portion of the flexible-walled tube, said pumping element comprising a pad extending generally in the longitudinal direction of said portion of the flexible tube and having a tube-engaging face, and a transverse rib on said tube engaging face; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump, the rib of the pumping element engaging the tube in each pumping cycle before the remainder of said tube-engaging face of said pad; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube; means interRelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position; and stroke adjustment means for varying the stroke of said pumping element, said pumping element engaging the tube only by said transverse rib in the position of said adjustment means corresponding to minimum pumping stroke.
 2. Pump as claimed in claim 1, wherein the said first and second operating means include respective rotary cams and respective pivoted lever arms engageable by the rotary cams and carrying the pumping element and the respective closure elements, the pivot axis of each said lever arm being disposed between said portion of said flexible tube and that part of the said lever arm which engages the respective rotary cam.
 3. Pump as claimed in claim 1, wherein the pump has a housing and comprises an anvil member having an anvil surface upon which the said portion of said flexible-walled tube lies and against which said tube is pressed when engaged by the pumping element and by the respective closure elements; and means mounting said anvil member in said housing removable as a unit from said housing permitting access to the flexible-walled tube.
 4. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube, said second operating means including pivoted lever arms, respectively; means pivotally connecting each respective closure element to the respective lever arm for rocking movement about an axis parallel to the pivotal axis of said lever arm; means resiliently biasing said lever arms to urge the respective closure elements into pinching engagement with said portion of the tube, and rotary cams engaging said lever arms, respectively, and adapted to rock the latter in opposition to their resilient biasing means to effect reciprocation of the closure elements upon rotation of said cams; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position.
 5. Pump as claimed in claim 4 wherein the first operating means for reciprocating the pumping element comprise a lever arm carrying the pumping element, means resiliently biassing the lever arm to urge the pumping element into engagement with said portion of the tube and a rotary cam engaging said lever arm and adapted to rock the latter in opposition to said resilient biassing means to reciprocate the pumping element upon rotation of said cam, and a common shaft supporting the respective lever arms of said first, and second operating means for rocking movement about the axis of said common shaft.
 6. Pump as claimed in claim 5, including a common cam shaft supporting the respective cams of said operating means.
 7. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating wiTh a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted on either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow there through and open positions in which said closure elements permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position; eccentric release cam means; and means rotating said release cam means to effect simultaneous movement of the pumping element and the two closure elements out of engagement with said portion of the tube to facilitate replacement of the tube, said release cam means being out of engagement with said pumping and closure elements during normal operation of the pump.
 8. Pump as claimed in claim 7, comprising a removable anvil member having a surface upon which rest the portions of the flexible-walled tube engageable by said pumping and closure elements when the anvil member is in a normal operative position; and latching means retaining said anvil member in said operative position, said latching means being releasable automatically when said pumping element and said closure elements are out of engagement with said tube to permit removal of the anvil member.
 9. Pump as claimed in claim 7, wherein said first operating means include a lever arm carrying the pumping element; and comprising means for varying the stroke of said pumping element including a presettable rotatable cam engageable with said lever arm, said presettable rotatable cam comprising part of said release cam means and including a common adjusting member operatively connected to both said rotatable cam and the release cam means for selective adjustment thereof.
 10. Pump as claimed in claim 7, comprising a housing provided with an opening; a removable anvil member; means mounting said anvil member in said housing removable from said housing through said opening, said anvil member, in its fully mounted position in said housing, supporting the portions of said flexible-walled tube with which said pumping and closure elements cooperate.
 11. Pump as claimed in claim 10, wherein said anvil member includes means for retaining said flexible walled tube thereon in contact with an anvil surface of said anvil member, so that the tube is removable for inspection together with said anvil member, when said pumping and closure elements are out of engagement with said tube.
 12. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump, said first operating means including a lever arm carrying said pumping element; means resiliently biasing said lever arm to urge said pumping element into engagement with said portion of the tube; a rotary cam engaging said lever arm and adapted to rock the latter in opposition to said resilient biasing means for reciprocating said pumping element upon rotation of said cam, and a presettable rotatable cam engageable with said lever arm and determining the stroke of said pumping element in operation of the pump; inlet and outlet closure elements mounted on either side of the pumping element; twO second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position.
 13. A pump of the peristaltic type which effects pumping by the deformation of a flexible-walled tube, comprising, a pumping element cooperating with a portion of the flexible-walled tube; first operating means for reciprocating the pumping element so as cyclically to pinch and release said portion of the tube, thereby to effect pumping and induction strokes successively of the pump; inlet and outlet closure elements mounted to either side of the pumping element; two second operating means for effecting reciprocation of said inlet and outlet closure elements, respectively, between respective closed positions in which said closure elements pinch the tube to prevent flow therethrough and open positions in which said closure elements permit flow through the tube; means interrelating the operation of said first and second operating means so that during pumping strokes of the pumping element the inlet closure element is in its closed position and the outlet closure element in its open position, while during induction strokes the inlet closure element is in its open position and the outlet closure element in its closed position, a housing enclosing said pumping and closure elements and provided with an opening; a removable anvil member; means mounting said anvil member in said housing slidable into and slidable out of said housing through said opening, said anvil member, in its fully mounted position in said housing, supporting theportions of said flexible-walled tube with which said pumping and closure elements cooperate, and means on said anvil member for retaining said flexible-walled tube in contact with said anvil surface, whereby the length of said tube with which said pumping and closure elements cooperate is removable from said housing along with said anvil member. 